The present invention relates to a high-frequency signal processing device having a frequency synthesizer (PLL: Phase-Locked Loop) and to a wireless communication system. For example, the present invention relates to a high-frequency signal processing device performing modulation/demodulation using a frequency synthesizer and to a wireless communication system such as a mobile terminal etc. having the high-frequency signal processing device.
For example, International Application Publication No. WO2012/101774 (Patent Document 1) teaches a method of suppressing frequency fluctuations by switching capacitors of an oscillation circuit upon varying load (including switching current) of the oscillation circuit. Japanese Patent Application Laid-Open Publication No. 2005-109618 (Patent Document 2) teaches an automatic switching circuit for finding an optimum frequency band while switching frequency bands of a VCO by the binary search method. In addition, Ting Wu; Un-Ku Moon; Mayaram, K., “Dependence of LC VCO Oscillation Frequency on Bias Current,” IEEE International Symposium on Circuits and Systems, May 2006 (Non-Patent Document 1) describes a theory of frequency fluctuation by increases in current. Groszkowski, J., “The Interdependence of Frequency Variation and Harmonic Content, and the Problem of Constant-Frequency Oscillators,” Proceedings of the Institute of Radio Engineers, Vol. 21, No. 7, pp. 958-981, July 1933 (Non-Patent Document 2) describes a theory of oscillation frequency fluctuation by harmonics.